Casting metals in metal molds or dies



Oct. 24, 1933- F. w. MOCONNEL 1,931,587

CASTING METALS IN METAL MOLDS 0R DIES Filed Jun'e 30, 1931 Patented Oct.24, 1933 PATENT OFFICE CASTING METALS IN METAL MOLDS OR DIES FredericWhigham McConnel, Barbers, Martley, England, assignor to Metal CastingsLimited, Worcester, England, a British company Application June 30,1931, Serial No. 547,843, and in Great Britain July 26, 1930 2 Claims.

This invention is for improvements in casting metals in metal molds ordies (whether the metal is run into the die under pressure or undergravity only) and thus casting objects which have pro- 5 jectingportions, or recesses, which make it a matter of d'filculty to withdrawthe core from the interior of the cast article, or to remove the latterfrom the die. Such a difliculty occurs in the die-casting of aluminiumalloy pistons, in

0 which the inwardly projecting gudgeon-pin bosses make it difiicult towithdraw the metal core from the interior of the cast piston. Usuallythe pistons are cast skirt uppermost, and no attempt is made to die-castthe piston-ring grooves. The difliculty of withdrawing the core hashitherto been combated by making the core in three or more pieces allextending the full length of the piston, viz two cheeks, in which areformed the recesses for the gudgeon pin bosses,

and a central key-piece by which the cheeks are spaced apart, the flanksof this key-piece being tapered from the skirt end (which is uppermostwhen casting) down to the crown-end. The core is assembled and placed inthe die, and after the piston has been cast the key-piece is withdrawn.

This permits the two cheeks to be moved inwards towards each other clearof the gudgeon pin bosses and then withdrawn from the piston. With sucha core the difliculty occurs that in course of time the sharp edges ofthe contacting faces of the cheeks and key-piece become rounded andhence in casting, a flash (i. e. a projecting ragged edge of metal) iscast onto the interior of the piston in the fillet formed by theserounded edges. and this flash embracing the peripheral edges of thecheeks as it does, prevents them from being moved in towards each otherto clear the gudgeon pin bosses.

It will readily be appreciated that this formation of flash is notlimited to the particular casting operations described above, nor is itsformation limited to cores, but it will occur also on dies where loosepieces are used, and the present invention has for its chief object toprovide a methi5 od of die-casting free from this disability.

The method provided by this invention consists in utilizing a mutilatedcore or die in conjunc-.

tion with a renewable and removable loose piece' (or pieces) which goesto complete the core or die i0 and is formed previously by die-castingon to it.

A mutilated core or die is one which is incomplete in some essentialfeature, for example a mutilated core for a piston may be minus thoseportions (having two opposed recesses) in which 5 the gudgeon pin bossesare formed.

In one form the invention is applied to the diecasting of a hollowarticle, such as a piston, having interior projections which wouldprevent the w.thdrawal of a solid core. In carrying out this applicationof the invention a mutilated core is an employed, the mutilated partbeing confined to those portions of the core which will be overhung bythe projections in the casting and which would, if the core was solidthroughout, prevent removal thereof. Loose pieces corresponding to themutilated part of the core are die-cast by using the mutilated core, towhich they are complementary, as a portion of the die for casting.

The core thus completed is used in the ordinary way in the known processof die-casting, and after the completion of the casting operation, themutilated core iswithdrawn, leaving the loose-pieces in situ but freefor subsequent removal.

This invention also provides a method of diecasting articles,particularly pistons, which consists in the utilization of a mutilatedcore, completing said mutilated core by casting on to it one or moreloose-pieces, employing the core thus completed in the known process ofdie-casting, and withdrawing the mutilated core from 0 the cast objectleaving the loose-pieces in situ for subsequent removal.

One method of die-casting pistons according to the present inventionwill now be described in detail with reference to the accompanying draw-35 ing, in which:-

Figure 1 is a cross-section through a die, showing the mutilated coreand the piston,

Figure 2 is a cross-section through the die for casting the loose-pieceson to the mutilated core and,

Figure 3 is a perspective view of the mutilated core and theloose-pieces.

Throughout this description like reference numerals indicate like parts.

The metal piston-die shown in Figure 1 is divided into two portions 10and 11, the joint face between them lying on the axis of the piston 12.The mutilated core 13 consists of a barrel-shaped portion 14 for theskirt of the piston, and, at its inner end a web 15 which is of the samewidth as the gap between the piston bosses 16. It will be appreciatedthat as no part of the mutilated core is overhung by the bosses 16, thecore may easily be withdrawn from the piston after casting. The core iscompleted by two loose-pieces 17 which fit on opposite sides of it. Onehalf of the recess for a piston boss is formed in a loosepiece as at 18and the other half in the mutilated core as at 19. Each loose-piece isformed with a dove-tailed projection 20 which is arranged to engage in adove-tailed slot 21 in the mutilated core 13. The die-casting of thepiston is carried out in the ordinary manner, metal being run in througha runner 22. When the casting has been effected, the mutilated core 13is withdrawn, the two halves 10 and 11 of the die broken apart and thepiston 12 removed and the two loose-pieces 1'7 moved in towards eachother so that they may be withdrawn between the gudgeon pin bosses 16.

The manner in which the loose-pieces are cast on to the mutilated core13 is illustrated in Figure 2. The core 13 is inserted in a die 23having a runner 24. Pins 25 having conical projections 26 whichcorrespond in shape to the gudgeon pin bosses 16 are inserted one fromeach side of the die. The loose-pieces are then cast in the ordinarymanner.

One advantage of this method is that any wear which occurs on the mainsolid part of the core is built up each time the loose-pieces are caston to it. If, as is preferred, the loose-pieces are cast from an alloyof the same analysis as that from which the piston is cast, badcastings' may be remelted without the removal of the loosepieces (whichmay have become locked in position) without entailing the introductionof foreign matter to the alloy. If undamaged the loose-pieces may beused several times. Normally, a small stock of loose-pieces will be castoif each mutilated core and used as and when required.

For forming the piston-ring grooves, a previously cast ring 2'7 isfitted into the die 10, 11, so that it projects as a flange into thebore of the die. This ring will remain in the piston when the latter iswithdrawn from the die, and is subsequently broken out. In order tofacilitate breaking, the ring may be slotted partly through.Alternatively, this ring 27 may be cast in situ in the die 10, 11 butthe first method is preferred, particularly when the piston is to beformed with more than one piston-ring groove.

As indicated herein, the invention is not limited to the die-casting ofpistons. It may be applied to the casting of any article which hasprojections or recesses which would prevent the removal of the core fromthe cast article or the removal of the latter from the die.

I claim:--

1. A core for die casting hollow articles having internal projections,comprising a main body portion adapted to be drawn as a unit from thehollow article after casting and to be used in a plurality of castingoperations, means on said body portion for releasably holdingsupplemental core elements thereto, and a plurality of supplemental coreelements of a shape to form at least a portion of the internalprojections on said casting and die cast onto said holding means.

-2. A core for die casting hollow artitcles having internal projections,comprising a main body portion adapted to be drawn as a unit from thehollow article after casting and to be used in a plurality of castingoperations, means on said body portion for releasably holdingsupplemental core elements thereto and a plurality of supplemental coreelements of a shape to form at least a portion of the internalprojections on said casting and die cast onto said holding means, saidsupplemental core elements being formed of meta1 similar to that in thecast article.

FREDERIC WHIGHAM McCONNEL.

